Due to their increased wavelengths, low frequencies usually require large drivers (e.g., subwoofers) to generate higher volume. In vehicle and home stereo applications, large amplifiers are used to drive large drivers (subwoofers), which have become very popular in car audio.
Many users of mobile devices, such as iPods, tablets, and smartphones, seek an immersive audio experience. Earbuds (i.e., headphones that fit directly in the outer ear) can be power efficient, but often lack drivers sufficiently powerful to create bass. On-ear (i.e., supra-aural) or over-the-ear headphones (i.e., circumaural) can incorporate larger drivers, but can be power hungry. On-ear and over-the-ear headphones can also seal the volume of air between the ear and the headphone to increase the reproduction of bass. Users of these designs perceive a bass experience when higher Sound Pressure Levels (“SPL”) are generated within the headphones by modulating the air volume between the ear and the headphones to recreate low frequency content. This reproduces an audio experience similar to what was initially recorded, but does not reproduce the same effect since the amount of air modulated is limited to that which is within the ear canal.
Increased SPL may contribute to the masking of certain sounds, thus affecting the overall auditory experience. Increased SPL can also cause temporary or permanent impairment over time.